It appears to me that the D7100 is everything an underwater shooter needs. It is not clear to me what one gives up in comparison to a "professional camera" like my D300. The 7100 has a weather sealed body and an AF system with the best. All I need to do is give up my compact flash cards and what else? The DPreview indicates that the D-7100 is at least equal to the d-600 overall according to my reading. (Your mileage may vary)

I did not know that it was such a fantastic camera. So a d800 in ikelite, would be much better then d7100 in aluminum housing. Or wait a year and then search for used aluminum housing ? Does the Tokuna 10 17 works with 1.4 teleconverter on the d800 ?

For the past year I have been shooting a D800 in an Ikelite housing (I just switched to an Aquatica housing). I have been VERY happy with the D800. My previous DSLR was the D300. I did not upgrade to FX until I could get a camera that had a sensor with a higher pixel density than the D300. That way, I was not "giving up" anything with respect to the magnification of my macro lenses. I can crop any part of one of my FX images from my D800 to mimic the 1.5 crop factor of a DX sensor, and still have more pixel info and resolution than the complete RAW file from my D300. Also, the corner sharpness of my W/A images is superior.

The real question for a macro shooter is the D800 pixel density (cropped 1.5) better than the D7100?

Tom

If purchasing a camera body denovo, and you are committed to continue using the DX format or don't shoot W/A, then the D7100 would be superior to the D800 in pixel density. In DX mode, the D800 produces a 14 BIT RAW file size of 18.6 MB. Whereas the D300 produces a 14.9 MB file, and the D7100 produces a 28.5 MB file. In FX mode, the D800 produces a 14 BIT RAW file size of 41.3 MB. I use a D7100 on a 400mm f/2.8 lens for a lot of my dangerous game photography (because of it's relatively high pixel density and crop factor ). As far as fit and finish, the D800 is a high-end prosumer level camera and the D7100 is a midrange. Nikon's last professional level DX camera (the D2XS) hit the market June 1, 2006. Nikon's last prosumer level DX camera (the D300S) launched July 30, 2009. It remains to be seen if Nikon will produce any further midrange DX cameras after the D7100 (which launched Feb. 21 2013). It appears the DX format is being marginalized towards the entry level cameras (at the very least). This is EXACTLY how Nikon phased out non-autofocus, non-auto exposure, non-lens indexing and non-internally metered cameras. The cameras lacking the new feature (or format) first disappear from the top tier cameras, and Nikon just works it's way down the list. BYE-BYE DX DSLR. Reading these tea leaves caused me to decide not to put any more dollars into the DX format lenses, and switch to a FX body for my U/W work. I also shoot a lot of W/A, which was another win for FX format as far as I was concerned.